Was there ever a diecast car made for the 1966 galaxie 500 convertible?

No, not originally. That year the Galaxie and full size Fords were available in 19 different modles with seven differnt body designs: LTD, Galaxie 500XL, Galaxie 500 L, Galaxie 500, and Custom 500 with hardtop, sedans, and convertible styles. The diecast was not originally put o the regular Galaxie 500, but I know it was on the LTD and 7 Litre